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Saturday, 15 August 2015

Living planet: lightning

Discounting humans almost all forest fires are
caused by lightning, which strikes the planet 100 times a second, or 3 billion
times a year.The lightning also
converts atmospheric nitrogen intoa
form which can be used by life. Without these strikes it is questionable
whether plants and animals would have appeared, or anything that we would
recognize as a thriving biosphere.

Apart from joining with thunder to create awe and wonder in the consciousness
of sentient beings witnessing a thunderstorm lightning has physical effects
which are, and for millions of years have been, of critical importance to the
biosphere.

First, the heat generated in the air (comprising
78% nitrogen) breaks down the triple
bond which holds togetherthe 2 nitrogen
atoms in each molecule of nitrogen so tightly that they cannot be used by the
living organisms which need them. Without this bond being broken down there
would be no life.There also has to be
rain to dissolve the nitrogen atoms and take them down to the soil where they
can be acted upon by bacteria and taken into the cycle of processes by which
plants are made. Animals and humans eat the plants, so they depend on the same
nitrogen atoms released from the triple bonds.

(The whole process by which nitrogen is taken from the atmosphere, used by the living world, and returned to the atmosphere is known as the nitrogen cycle. This feedback mechanism has kept the optimum concentration of nitrogen in the air at 78 % over millions of years.)

There is another way in which the triple bonds
holding N (nitrogen) atoms together can be broken. This requires the action of bacteria on
the tightly bonded molecules to produce ammonia . Ammonia contains 1 N atom and
4 H (hydrogen) atoms but the N is easy to extract from the ammonia for use by
living systems.Thisprocess does not appear to involve lightning
but is this really the case? It requires bacteria to produce the ammonia; yet
bacteria are living organisms and all organisms require N freed from its triple
bond.

I am not a qualified biologist so please pull me up
if I am wrong but it does seem to me that without lightning there would have
been no bacteria to extract N from the atmosphere for use by other bacteria in the
first step of the proteinbuilding
process on which plants and, ultimately, animals depend. If this is right then all living systems, from microbes to mammals,
depend on lightning strikes, either taking place now or having done so in the
remote past.

Some scientists speculate that electrical discharges
in the primeval atmosphere, consisting of water vapour, ammonia and carbon
dioxide, somehow sparked off a process
which led to living organisms. The odds against this are breathtakingly astronomical unless
one invokes the quantum realm and this means bringing in agents outside the
natural order of objective, directly empirically testable science.

Returning to the present biosphere lightning is the main
cause of wildfires, apart from human beings in the geologically very recent past
. This is another way in which electrical discharges are an indirect but important
agent in the living world.Forest fires remove various growth inhibitors
and infuse the soil with water-retaining, mineral –rich charcoal. The fires
also facilitate the growth of fungi which help produce more nitrogen in the
form which is right for life.

Finally, lightning and rain cooperateto reduce air pollution. The sparks fuse dust
and pollen particles together, making them heavier and able to be washed out of
the atmosphere. This is why the air is fresherfollowing a thunderstorm than
after ordinary rain.